legs of runner using exercise for depression
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It’s safe to say everyone knows about the benefits of exercise, but not everyone knows there’s a relationship between depression and exercise. We all know exercise helps keep our bodies strong and healthy. It’s good for our muscles, bones, and joints. We also know it’s good for our overall wellbeing. Getting enough exercise every day can improve our sleep, improve our mood, improve our mental clarity, problem-solving skills, and simply make us feel better overall.

Here’s something it’s important for anyone reading this article to understand:

Evidence shows that for people with depression, exercise is effective in reducing the severity and frequency of depressive symptoms.

Consider these studies:

Finally, in an article published by the Harvard Medical School in 2021 called “Exercise is an All-Natural Treatment to Fight Depression,” Dr. Michael Craig Miller explains:

“In people who are depressed, neuroscientists have noticed that the hippocampus in the brain—the region that helps regulate mood—is smaller. Exercise supports nerve cell growth in the hippocampus, improving nerve cell connections, which helps relieve depression.”

The data are in and the evidence is clear and irrefutable: people with depression can benefit from an exercise routine. But the question remains: exactly how much?

Depression and Exercise: How Much Exercise Do You Need to Reduce Depressive Symptoms?

We published an article recently called “Physical Activity and Depression Among Older Adults.” In that article, we report that researchers showed that for older adults, around an hour and a half of moderate aerobic activity per week reduced depressive symptoms. That finding intrigued us, because that’s about half of the daily amount of exercise recommended by the Centers for Disease Control (CDC) for optimal health.

To follow up on that interesting information and learn more, we searched for similar articles on the impact of exercise duration on depression for people in all adult age groups, rather than studies limited to seniors and older adults. We found an article that addressed our interest. The study “Association Between Physical Activity and Risk of Depression – A Systematic Review and Meta-Analysis” used data from close to twenty thousand patients – comprising over two million person-years – to answer this question:

What is the dose-response association between physical activity and incident depression in adults?

Or, in plain language:

How much exercise do you need to reduce risk of developing depression?

That’s exactly what we want to know. First, though, let’s look at what the CDC says about exercise and physical and mental health.

The CDC Guidelines for Exercise and Activity

The CDC released their first set of guidelines of physical activity and exercise in 2008 in a publication called “2008 Physical Activity Guidelines for Americans.” In 2019, they updated those guidelines with their publication of “Physical Activity Guidelines for Americans, 2nd Edition.” The second set of guidelines reiterates the importance of exercise for all people of all ages, and includes insights from the most recent research on the overall health benefits of exercise.

CDC 2019: Recently Identified Benefits of Exercise

  1. Decreased likelihood of various forms of cancer
  2. Benefits for the brain:
    1. Enhanced cognition
    2. Better sleep
    3. Improved overall wellbeing
  3. Among patients with long-term medical issues:
    1. Decreased likelihood of premature disease-related mortality
    2. Increased over physical ability
    3. Enhanced quality of life
  4. For pregnant women:
    1. Decreased weight gain
    2. Reduced likelihood gestational diabetes
    3. Decreased incidence perinatal and/or postpartum depression
  5. For youth:
    1. Better bone health
    2. Appropriate age/height/weight relationship
    3. Enhanced cognition

Next, they offered suggestions on how much exercise, per week, each person needs to achieve optimal health.

CDC 2019: How Much Exercise Do You Need?

Advice for Adults

The CDC advises adults to spend more time moving, and less time sitting. Any amount of physical activity is preferable to no activity, and any amount of time spent participating in even light or moderate activity is more beneficial than sitting on the couch. A combination of moderate, moderate-to-vigorous, or vigorous activity is best.

To get the most out of an exercise routine, the CDC advises:

  • Moderate aerobic exercise: 2.5 to 5 hours every week
    • Moderate aerobic exercise means doing activities like walking, swimming, or slow jogging at a sustainable pace
  • Vigorous aerobic exercise: 1 to 2.5 hours every week
    • Vigorous aerobic exercise means doing activities like walking, swimming, or running as a challenging pace
  • Some mix of vigorous or moderate aerobic exercise that meets the time requirements in the two bullet points above

Advice for Everyone

  • It’s better to do a little bit every day than cram exercise in on the weekends or 1-2 days a week
  • More exercise/more benefit: it’s okay to do more than the CDC guidelines, but listen to your body, don’t overdo it, and ask your doctor if you have any doubts
  • Weights/resistance: it’s important to add weight training or functional resistance exercises – i.e. pushups, planks, etc. – at least twice a week.

Advice for Seniors

The CDC suggest older adults and seniors:

  • Add balance exercises to any exercise routine
  • Keep performing moderate aerobic activity
  • Keep performing vigorous aerobic activity as possible
  • Should stay within themselves, and only attempt activity appropriate to their current ability
  • Should consult their doctors before beginning an exercise routine if they have a chronic illness or medical condition
  • Do what they can: if it’s not possible to meet the guidelines, it’s important to start with what’s possible, and move up from there

Advice for Everyone: Safe Exercise Tips

To avoid injury, have fun, and exercise safely:

  • Know there are risks, but also understand anyone of any age and any fitness level can enjoy the benefits of exercise
  • Choose types of exercise that are fun, age-appropriate, and not beyond personal capability
  • People new to exercise or returning to exercise should start easy, build slowly, and understand that it takes time and consistent effort to meet any exercise goals

The general idea the CDC espouses is that anything is better than nothing. To get the most out of exercise, people in the general population should follow the guidelines above. Now we’ll move on form these general recommendations and look at the study we introduced above, in order to learn how much exercise people with depression need to experience symptoms reduction.

Depression and Exercise: Conclusions From the Study

In this study, researchers wanted to know how much exercise people need to prevent depressive episodes, prevent major depressive disorder, and prevent an escalation or elevation of existing depressive symptoms.

To achieve this goal, researchers analyzed data from 15 studies including data from 191,130 participants, 28,806 incidents of depression, and over 2 million person-years. A person-year refers to a combination of the number of participants in a study and how long they stay in the study. For instance, a one-year study with one hundred people would total 100 person-years, and a two-year study on two hundred would total 400 person-years.

The size of this study – close to 200,000 people with 2 million person-years – make it significant. Compared to the study on the impact of physical activity on older people with depression, which included data on around 500 people, this study allows the researchers to make population-level conclusions based on the data.

The research team used three levels of exercise exposure (i.e. exercise amounts) as metrics:

  1. Low level of exercise: 4.4 mMET hours per week, which corresponds to roughly half of the CDC-recommended amount of weekly exercise
  2. Moderate, recommended level of exercise: 8.8 mMET hours per week, which corresponds to the the CDC-recommended amount of weekly exercise
  3. High level of exercise: 17.5 mMET hours per week, which is roughly double the the CDC-recommended amount of weekly exercise

In addition, the team used three outcome measures to asses the impact of exercise on depression:

  1. Incidence of depressive episode
  2. Presence of major depressive disorder
  3. Increase in symptom severity

Finally, the team calculated the level of population risk associated with the impact of depression on exercise. Let’s take a look at the data.

Results: Depression, Depressive Symptom Severity, and Amount of Exercise

Incidence of Depression

  • Low level of exercise:
    • 18% lower risk of depression, compared to no exercise
  • Moderate, recommended level of exercise:
    • 25% lower risk of depression, compared to no exercise
  • High level of exercise:
    • 28% lower risk of depression, compared to no exercise

Incidence Major Depressive Disorder (MDD)

  • Low level of exercise:
    • 17% lower risk of MDD, compared to no exercise
  • Moderate, recommended level of exercise:
    • 25% lower risk of MDD, compared to no exercise
  • High level of exercise:
    • 26% lower risk of MDD, compared to no exercise

Depressive Symptom Severity

  • Low level of exercise:
    • 20% lower risk of increased symptom severity, compared to no exercise
  • Moderate, recommended level of exercise:
    • 27% lower risk of increased symptom severity, compared to no exercise
  • High level of exercise:
    • 30% lower risk of increased symptom severity, compared to no exercise

This information is crucial for people with depression considering supplementing their treatment with exercise. The data shows that engaging in half the amount of exercise recommended by the CDC results in significant reduction of likelihood of incident depression, major depressive disorder, and an increase in depressive symptom severity.

Now let’s look at the data on population. What these figures measure is the percentage of outcomes (incident depression, MDD, increased symptom severity) that could have been avoided if all adults engaged in one of three levels of activity (low, moderate, or high).

Results: Amount of Exercise and Depression Risk, Population Level

Incidence of Depression

  • If all adults engaged a low level of exercise:
    • 6.8% of cases of depression could have been prevented
  • If all adults engaged in the moderate, recommended level of exercise:
    • 11.5% of cases of depression could have been prevented
  • If all adults engaged in a high level of exercise:
    • 13.9% of cases of depression could have been prevented

Incidence Major Depressive Disorder (MDD)

  • If all adults engaged a low level of exercise:
    • 2.9% of cases of MDD could have been prevented
  • If all adults engaged in the moderate, recommended level of exercise:
    • 7.3% of cases of MDD could have been prevented
  • If all adults engaged in a high level of exercise:
    • 8.0% of cases of MDD could have been prevented

Depressive Symptom Severity

  • If all adults engaged a low level of exercise:
    • 9.4% of cases of elevated symptom severity could have been prevented
  • If all adults engaged in the moderate, recommended level of exercise:
    • 14.4% of cases of elevated symptom severity could have been prevented
  • If all adults engaged in a high level of exercise:
    • 17% of cases of elevated symptom severity could have been prevented

This data is also crucial: it shows us the “what if…” component of the impact exercise on rates of depression. We’ll explain below.

What if Everyone Got the Recommend Amount of Exercise?

If all adults got the recommended amount of exercise, how many fewer people would have had depression?

We can use the available data and extrapolate. The 2021 National Survey on Drug Use and Health (2021 NSDUH) indicates that 21 million adults in the U.S. had major depressive disorder. Using the figures above, we reach the following conclusions:

  • If all adults engaged a low level of exercise: (21,000,000) x (0.029) = 629,000
More than 500,000 cases of MDD might have been prevented if people exercised at least 1-2 hours per week.
  • If all adults engaged in the moderate, recommended level of exercise: (21,000,000) x (0.073) = 1,533,000
Over 1.5 million cases of MDD might have been prevented if people exercised at least 3.5-7 hours per week
  • If all adults engaged in a high level of exercise: (21,000,000) x (0.08) = 1,680,000
Over 1.6 million cases of MDD could have been prevented if people exercised 7-14 hours per week

Since we don’t have data on the number of people who did not exercise who experienced an increase in symptom severity, we can’t make the same calculations to determine how many people currently in treatment might prevent an escalation in symptoms by adding a moderate level of exercise to their treatment plan. However, based on the data in the study, we can conclude the following:

If we had 100 patients with depression, and they all engaged in the following levels of exercise:

  • Low level: 9 fewer patients might experience symptom escalation
  • Moderate level: 14 fewer patients might experience symptom escalation
  • High level: 17 fewer patients might experience symptom escalation

If we combine those potential successes with the successes associated with traditional treatment with psychotherapy, medication, and lifestyle changes, we see the potential for improving patient outcomes across the board.

The bottom line?

Exercise works as an adjunct, auxiliary treatment for depression – and the more exercise, the better.